PROJECT SUMMARY/ABSTRACT Wealth inequality has long been linked to adverse health outcomes such as higher mortality, obesity, and illness. Importantly, a growing literature also links inequality to declines in vital forms of social functioning and wellbeing. Having less than others, and especially perceiving that the disparity is unjustified, makes individuals less prosocial and more mistrusting, aggressive, intolerant, and risk seeking. Yet little is known about how the experience of inequality impacts social functioning and wellbeing in early childhood. What little work exists on this topic has been correlational in nature and has used measures of socioeconomic status rather than inequality, thus precluding causal conclusions about the impact of inequality. Further, prior work has not addressed how children's perception of inequality as justified versus unjustified impacts their social behaviors. The current proposal seeks to elucidate these questions, with a focus on the effects of inequality on 6-9-year- old children's prosocial behavior. The proposed studies will use an experimental approach to create inequality of resources between a participant child and an absent peer. In Study 1, children will either receive fewer resources than the peer, more than the peer, or the same as the peer, or fewer resources in a nonsocial context. Subsequently, children's prosocial (helping) behavior towards a researcher will be assessed. This first study will establish how experiencing inequality, and specifically having less than others, impacts children's prosocial behavior. In Study 2, children will experience either justified inequality (receiving less than the peer after performing worse than the peer on a task), unjustified inequality (receiving less than the peer after performing better than the peer), or justified equality (receiving the same as the peer after performing as well as the peer). Again, children's prosocial (helping) behavior will subsequently be assessed. This study will establish how unjustified inequality in particular impacts children's prosocial behavior. This research will lay the foundation, establish a set of tasks, and obtain a first set of findings that will serve a larger research program on the near-term and long-term impact of inequality on children's social development and wellbeing. The ultimate goal of this work is to attenuate the adverse effects of inequality on children's social behaviors and developmental outcomes, thus contributing to their long-term health and wellbeing.